Chronic obstructive pulmonary disease (COPD) affects 15 million patients in the U.S. and is the sixth leading cause of death. It is characterized by the retention of mucus secretions in the lungs. Many patients diagnosed with COPD have a disorder called chronic bronchitis (CB), and 600,000 patients are hospitalized each year due to an acute exacerbation of CB. Cystic fibrosis and Primary Ciliary Dyskinesia (PCD) are other examples of lung disorders that have a clinical profile similar to COPD. Ciliary dyskinesia, whether primary or secondary, results in retained secretions that can only be cleared by coughing.
Another disease state characterized by the accumulation of retained mucous secretions is sinusitis. Sinusitis is an inflammation of the paranasal sinuses typically associated with an upper respiratory infection. It is this country's most common health-care complaint, affecting an estimated 31 million people. (A. Moss and V. Parsons, National Center for Health Statistics, 1986: 66–7, DHHS Publication No. (PHS)86-1588 (1985)).
Otitis media (OM) is a viral or bacterial infection of the middle ear that primarily afflicts children under the age of three. It is usually precipitated by an upper respiratory infection that spreads into the middle ear via the nasopharynx and eustachian tube. Approximately 25–50 million office visits are made each year for diagnosis and treatment of OM. By age three, about 75% of children will have had at least one episode of acute OM (J. Klein, Clin. Infect. Dis. 19, 823–33 (1994)). Following appropriate treatment with antibiotics, accumulated fluid in the middle ear remains, causing hearing impairment and potential language and cognitive development delays. Enhanced ability to clear secretions in the middle ear would reduce or eliminate significant sequelae of otitis media.
An additional disorder resulting from retained secretions is pneumonia. Patients who are immobilized for a variety of reasons are at high risk for developing pneumonia. Despite extra vigilance and numerous interventions, pneumonia develops in over 400,000 patients per year, with significant morbidity and mortality.
There are also situations where it is therapeutically desirable to increase drainage of the lacrimal system. When the lacrimal drainage system is not functioning properly the result can be excessive tearing (epiphora), mucopurulent discharge, and recurrent dacryocystitis. Current treatments for nasolacrimal duct obstruction are mostly invasive surgical procedures, and researchers have sought to discover noninvasive pharmaceutical treatments.
Tear secretion can be stimulated from lacrimal accessory tissues via P2Y2 and/or P2Y4 purinergic receptor-mediated mechanisms similar to those which hydrate airway epithelia. Dry eye disease is the general term for indications produced by abnormalities of the precomeal tear film characterized by a decrease in tear production or an increase in tear film evaporation, together with the ocular surface disease that results. Currently, the pharmaceutical treatment of dry eye disease is mostly limited to administration of artificial tears (saline solution) to temporarily rehydrate the eyes. However, relief is short lived and frequent dosing is necessary.
Secretory functions of the uterine, cervical and vaginal mucous cells have a profound impact on the function and health of the reproductive tract. For example, the quality and quantity of cervical mucus changes throughout the menstrual cycle and such changes dramatically influence fertility. Under the influence of rising estrogen levels, cervical mucus becomes thin, allowing the passage of spermatozoa. Later in the menstrual cycle, as progesterone levels increase, mucus becomes thick and hostile to sperm penetration, thereby closing the window of fertility. Such thickening of cervical mucus is thought to be one of the primary modes of contraceptive action for progestin-only contraceptives.
Estrogen stimulates the production of thin, isotonic mucus, with increased amounts of high molecular weight glycoproteins. Cervical mucus contains 98% water at mid cycle and 90% at other times. Cervical mucus is also rich in metallic ions, enzymes (such as alkaline phosphatase, etc.), soluble proteins and salts. The gel phase of cervical mucus contains high molecular weight glycoproteins called mucin. Mucin micelles cross-link by disulfide bridges. Estrogen and progesterone control the arrangement of these micelles. These micellar arrangements influence the rheological properties of mucus. See Kopito et al. Water and electrolytes in human cervical mucus. Fertil. Steril. 1973;24:499–506; Fordney-Settlage, D. A review of cervical mucus and sperm interactions in humans. Int. J. Fertil. 1981;26:161–169.
As estrogen levels fall during menopause, estrogen dependent tissue will start to involute and take on the characteristic appearance of estrogen deprivation. Cervical mucus levels diminish and vaginal mucosa regresses during menopause. With aging, the vagina becomes shortened, ruggae disappear, and elasticity is lost. Vaginal secretions become scanty. When estrogen is provided, some of these effects are reversed: the cervix starts to secrete some mucus and the vaginal mucosa regains its lost layers. However, the symptoms do not disappear completely, in part because the amount of estrogen provided for hormone replacement is lower than circulating estrogen levels during a normal menstrual cycle.
Approximately 40% of postmenopausal women experience atrophic vaginitis or vaginal dryness. During vaginal atrophy, the vaginal epithelium decreases in thickness, hydration, ruggae (folds), and blood flow. Causes of atrophic vaginitis include a decrease in the amount of estrogen present both locally and systemically as well as environmental factors such as chemotherapy, antihistamines, smoking cigarettes, excessive exercise, and vaginal products (i.e. douches, deodorants, and perfumes).
Estrogens or hormone replacement therapies cab be effective in reducing vaginal dryness. However, possible dangerous side effects include higher incidences of breast cancer, endometrial cancer, blood clots, nausea, breast tenderness, and headache. Products that are available over-the-counter include lubricants such as Astroglide and KY Lubricating Jelly as well as moisturizers such as Replens and KY Long Lasting Moisturizer. These products, which are mostly water in composition, provide only temporary relief (1–2 days) for symptoms and provide virtually no long-term benefits to the vaginal tissue.
Therefore, a need exists for new compositions and methods for modulating mucus production at mucosal surfaces.